In Part 1, we walked through the five essential steps for ordering and installing GCL pond liners — from ground prep to anchoring. In Part 2, we focused on what happens after the liner’s down, including tips for protecting it from UV, erosion, and construction damage.
Now in Part 3, we turn our attention to a less obvious but equally important aspect of GCL performance: wet and dry season cycling. This is especially relevant for projects in parts of Australia where liners may experience periods of drying followed by rehydration, either due to climate or temporary site exposure.
Note: When a GCL is properly covered and confined, seasonal wet and dry cycles — even in high-risk regions — generally do not impact its performance. The risks discussed in this guide mainly apply to temporarily exposed liners, delayed backfilling, or edges and overlaps that remain unprotected.
What is Wet-Dry Cycling?
Wet-dry cycling refers to the natural environmental process of a GCL being hydrated (swollen) during wet conditions, and then dried out (desiccated) during dry or uncovered periods. If this happens repeatedly — without the GCL being properly protected — it can lead to:
- Shrinkage or cracking of the bentonite layer
- Loss of swelling capacity (especially if calcium or saltwater is involved)
- Reduced barrier performance over time
In short, if your project is in a region with strong seasonal contrasts or if the liner will be exposed for any length of time, it’s worth understanding how to mitigate these effects.
Is This a Concern in Your Region?
Not all Australian climates affect GCLs the same way. Below is a quick guide to the relative wet-dry cycling risk by region:
|
Region |
Climate Characteristics |
Wet-Dry Cycling Risk |
Notes |
|
Northern QLD, NT, WA (e.g. Darwin, Cairns) |
Tropical: intense wet/dry seasons |
Very High |
Long dry spells followed by monsoon rain = extreme cycling |
|
Inland NSW, VIC, SA (e.g. Dubbo, Mildura) |
Semi-arid, high evaporation |
High |
Droughts followed by heavy summer rains |
|
Southern WA & VIC coasts (e.g. Perth) |
Mediterranean: wet winters, dry summers |
Moderate |
GCLs dry out over summer unless well covered |
|
Eastern seaboard (e.g. Sydney, Brisbane) |
Temperate/subtropical: steady rainfall |
Low–Moderate |
Cycling less common, but possible during site delays |
|
Tasmania |
Cool temperate: consistent moisture |
Low |
Rarely dries out fully, especially if covered |
Why Dry-to-Wet Transitions Are Riskier: The biggest risk occurs when a GCL dries out (from sun, wind, or delays), then is suddenly exposed to rainfall. Rehydration of cracked or unconsolidated bentonite can cause leaks or loss of material before the liner can reseal.
Key Maintenance Tips by Season
During Dry Periods
- Keep GCLs covered with at least 300 mm of moist soil or ballast as soon as possible after placement
- Avoid leaving GCL exposed to UV or wind for extended periods
- If self-sealing overlaps dry out before burial, rehydrate with clean water before backfilling
- Monitor for signs of surface cracking, especially on side slopes or wind-exposed areas
During Wet Periods
- Inspect covered areas for washouts or erosion, especially after heavy rain
- Check that soil cover has not slumped or exposed the liner
- Watch for soft spots or leaks near anchor trenches, pipes, or slope transitions
- Ensure slopes and cover soil are properly compacted to prevent ponding or sliding
Site Examples: What This Looks Like in Practice
- Tropical QLD Dam: GCL was placed during dry season but left uncovered for 3+ weeks. First rains caused cracking and minor bentonite loss at unconfined seams. Lesson: Always cover GCL immediately in tropical regions.
- Inland NSW Waste Cell: GCL installed in winter, fully covered. Site experienced summer drought but GCL remained stable thanks to well-compacted soil confining pressure.
- Perth Irrigation Pond: Edge laps dried out after liner delay. Team rehydrated overlaps before cover placement — successful reseal observed in post-rainfall inspections.
Studies support this: Research consistently shows that properly covered and confined GCLs are not affected by wet-dry cycling — even in high-risk zones. The damage occurs only when liners are exposed to drying and rewetting without protection.
Final Thoughts
Wet-dry cycling doesn’t always lead to failure — but it does create preventable risks if left unmanaged. Fortunately, with the right protective steps outlined above, even high-risk climates can support long-term GCL performance.
Think of this Part 3 guide as an extension of your installation checklist. If you’re working in northern or inland Australia, or leaving a liner exposed for longer than a day or two, it’s worth taking these seasonal effects into account.
Why InfraClay® Works
Our InfraClay® GCLs are engineered for reliable long-term performance in all Australian climates — from the tropics to the southern coast. Whether you're installing during the dry season or facing sudden rainfall, InfraClay's robust bentonite layer, reinforced carrier geotextiles, and strict manufacturing controls help it resist shrinkage, erosion, and permeability shifts under environmental stress.
If you're looking for a GCL that holds up across seasons — even with real-world construction delays — InfraClay® is built for it.
